linux-kernel - [PATCH v4 00/28] KVM: x86/mmu: TDX post-populate cleanups

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Message-ID: <20251030200951.3402865-1-seanjc@google.com>
Date: Thu, 30 Oct 2025 13:09:23 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Tianrui Zhao <zhaotianrui@...ngson.cn>, Bibo Mao <maobibo@...ngson.cn>, 
	Huacai Chen <chenhuacai@...nel.org>, Madhavan Srinivasan <maddy@...ux.ibm.com>, 
	Anup Patel <anup@...infault.org>, Paul Walmsley <pjw@...nel.org>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, Sean Christopherson <seanjc@...gle.com>, 
	Paolo Bonzini <pbonzini@...hat.com>, "Kirill A. Shutemov" <kas@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, loongarch@...ts.linux.dev, linux-mips@...r.kernel.org, 
	linuxppc-dev@...ts.ozlabs.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, x86@...nel.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>, 
	Kai Huang <kai.huang@...el.com>, Binbin Wu <binbin.wu@...ux.intel.com>, 
	Michael Roth <michael.roth@....com>, Yan Zhao <yan.y.zhao@...el.com>, 
	Vishal Annapurve <vannapurve@...gle.com>, Rick Edgecombe <rick.p.edgecombe@...el.com>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH v4 00/28] KVM: x86/mmu: TDX post-populate cleanups

Non-x86 folks, as with v3, patches 1 and 2 are likely the only thing of
interest here.  They make kvm_arch_vcpu_async_ioctl() mandatory and then
rename it to kvm_arch_vcpu_unlocked_ioctl().

As for the x86 side...

Clean up the TDX post-populate paths (and many tangentially related paths) to
address locking issues between gmem and TDX's post-populate hook[*], and
within KVM itself (KVM doesn't ensure full mutual exclusivity between paths
that for all intents and purposes the TDX-Module requires to be serialized).

I apologize if I missed any trailers or feedback, I think I got everything...

[*] http://lore.kernel.org/all/aG_pLUlHdYIZ2luh@google.com

v4:
 - Collect reviews/acks.
 - Add a lockdep assertion in kvm_tdp_mmu_map_private_pfn(). [Yan]
 - Wrap kvm_tdp_mmu_map_private_pfn() with CONFIG_KVM_GUEST_MEMFD=y. [test bot]
 - Improve (or add) comments. [Kai, and probably others]
 - s/spte/mirror_spte to make it clear what's being passed in
 - Update set_external_spte() to take @mirror_spte as well. [Yan]
 - Move the KVM_BUG_ON() on tdh_mr_extend() failure to the end. [Rick]
 - Take "all" the locks in tdx_vm_ioctl(). [Kai]
 - WARN if KVM attempts to map SPTEs into an invalid root. [Yan]
 - Use tdx_flush_vp_on_cpu() instead of tdx_disassociate_vp() when freeing
   a vCPU in VCPU_TD_STATE_UNINITIALIZED state. [Yan]

v3:
 - https://lore.kernel.org/all/20251017003244.186495-1-seanjc@google.com
 - Collect more reviews.
 - Add the async_ioctl() => unlocked_ioctl() patches, and use the "unlocked"
   variant in the TDX vCPU sub-ioctls so they can take kvm->lock outside of
   vcpu->mutex.
 - Add a patch to document that vcpu->mutex is taken *outside* kvm->slots_lock.
 - Add the tdx_vm_state_guard CLASS() to take kvm->lock, all vcpu->mutex locks,
   and kvm->slots_lock, in order to make tdx_td_init(), tdx_td_finalize(),
   tdx_vcpu_init_mem_region(), and tdx_vcpu_init() mutually exclusive with
   each other, and mutually exclusvie with basically anything that can result
   in contending one of the TDX-Module locks (can't remember which one).
 - Refine the changelog for the "Drop PROVE_MMU=y" patch. [Binbin]

v2:
 - Collect a few reviews (and ignore some because the patches went away).
   [Rick, Kai, Ira]
 - Move TDH_MEM_PAGE_ADD under mmu_lock and drop nr_premapped. [Yan, Rick]
 - Force max_level = PG_LEVEL_4K straightaway. [Yan]
 - s/kvm_tdp_prefault_page/kvm_tdp_page_prefault. [Rick]
 - Use Yan's version of "Say no to pinning!".  [Yan, Rick]
 - Tidy up helpers and macros to reduce boilerplate and copy+pate code, and
   to eliminate redundant/dead code (e.g. KVM_BUG_ON() the same error
   multiple times).
 - KVM_BUG_ON() if TDH_MR_EXTEND fails (I convinced myself it can't).

v1: https://lore.kernel.org/all/20250827000522.4022426-1-seanjc@google.com


Sean Christopherson (26):
  KVM: Make support for kvm_arch_vcpu_async_ioctl() mandatory
  KVM: Rename kvm_arch_vcpu_async_ioctl() to
    kvm_arch_vcpu_unlocked_ioctl()
  KVM: TDX: Drop PROVE_MMU=y sanity check on to-be-populated mappings
  KVM: x86/mmu: Add dedicated API to map guest_memfd pfn into TDP MMU
  KVM: x86/mmu: WARN if KVM attempts to map into an invalid TDP MMU root
  Revert "KVM: x86/tdp_mmu: Add a helper function to walk down the TDP
    MMU"
  KVM: x86/mmu: Rename kvm_tdp_map_page() to kvm_tdp_page_prefault()
  KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG_ON() condition
  KVM: TDX: Fold tdx_sept_drop_private_spte() into
    tdx_sept_remove_private_spte()
  KVM: x86/mmu: Drop the return code from
    kvm_x86_ops.remove_external_spte()
  KVM: TDX: WARN if mirror SPTE doesn't have full RWX when creating
    S-EPT mapping
  KVM: TDX: Avoid a double-KVM_BUG_ON() in tdx_sept_zap_private_spte()
  KVM: TDX: Use atomic64_dec_return() instead of a poor equivalent
  KVM: TDX: Fold tdx_mem_page_record_premap_cnt() into its sole caller
  KVM: TDX: ADD pages to the TD image while populating mirror EPT
    entries
  KVM: TDX: Fold tdx_sept_zap_private_spte() into
    tdx_sept_remove_private_spte()
  KVM: TDX: Combine KVM_BUG_ON + pr_tdx_error() into TDX_BUG_ON()
  KVM: TDX: Derive error argument names from the local variable names
  KVM: TDX: Assert that mmu_lock is held for write when removing S-EPT
    entries
  KVM: TDX: Add macro to retry SEAMCALLs when forcing vCPUs out of guest
  KVM: TDX: Add tdx_get_cmd() helper to get and validate sub-ioctl
    command
  KVM: TDX: Convert INIT_MEM_REGION and INIT_VCPU to "unlocked" vCPU
    ioctl
  KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()
  KVM: TDX: Don't copy "cmd" back to userspace for KVM_TDX_CAPABILITIES
  KVM: TDX: Guard VM state transitions with "all" the locks
  KVM: TDX: Bug the VM if extending the initial measurement fails

Yan Zhao (2):
  KVM: TDX: Drop superfluous page pinning in S-EPT management
  KVM: TDX: Fix list_add corruption during vcpu_load()

 arch/arm64/kvm/arm.c               |   6 +
 arch/loongarch/kvm/Kconfig         |   1 -
 arch/loongarch/kvm/vcpu.c          |   4 +-
 arch/mips/kvm/Kconfig              |   1 -
 arch/mips/kvm/mips.c               |   4 +-
 arch/powerpc/kvm/Kconfig           |   1 -
 arch/powerpc/kvm/powerpc.c         |   4 +-
 arch/riscv/kvm/Kconfig             |   1 -
 arch/riscv/kvm/vcpu.c              |   4 +-
 arch/s390/kvm/Kconfig              |   1 -
 arch/s390/kvm/kvm-s390.c           |   4 +-
 arch/x86/include/asm/kvm-x86-ops.h |   1 +
 arch/x86/include/asm/kvm_host.h    |   7 +-
 arch/x86/kvm/mmu.h                 |   3 +-
 arch/x86/kvm/mmu/mmu.c             |  87 +++-
 arch/x86/kvm/mmu/tdp_mmu.c         |  50 +--
 arch/x86/kvm/vmx/main.c            |   9 +
 arch/x86/kvm/vmx/tdx.c             | 659 ++++++++++++++---------------
 arch/x86/kvm/vmx/tdx.h             |   8 +-
 arch/x86/kvm/vmx/x86_ops.h         |   1 +
 arch/x86/kvm/x86.c                 |  13 +
 include/linux/kvm_host.h           |  14 +-
 virt/kvm/Kconfig                   |   3 -
 virt/kvm/kvm_main.c                |   6 +-
 24 files changed, 468 insertions(+), 424 deletions(-)


base-commit: 4cc167c50eb19d44ac7e204938724e685e3d8057
-- 
2.51.1.930.gacf6e81ea2-goog